Global warming is a looming catastrophe for California, the nation and the world, but few people — politicians and the general public alike — want to talk about it, Gov. Jerry Brown told a San Francisco conference on climate change Thursday.

Though no one can say when — or even if — a worst-case environmental disaster could occur, that’s no reason to avoid the discussion, he added.

“If it’s possible, we need to talk about it,” the governor told the standing-room-only crowd at the opening session of the 15th annual Navigating the American Carbon World conference at the South of Market InterContinental Hotel.

The gathering of climate-change activists was the friendliest of crowds for Brown, who received a standing ovation even before he gave his 20-minute talk. Relaxed and tieless, the governor warned the audience not to pay attention to accomplishments of the past.

Focusing on the future, particularly one with a potential for disaster, isn’t something most people are particularly good at doing, he said. Reports that the West Antarctica Ice Sheet is melting rapidly and warnings that the level of San Francisco Bay could rise by as much as 10 feet in the next century are getting far less attention than they deserve.

Most politicians believe the only real catastrophe is losing an election, Brown said.

Though efforts like California’s landmark emissions cap-and-trade program, which the governor is working hard to get reauthorized past 2020, and the 2015 Paris Agreement on cutting back greenhouse gases worldwide are important, they aren’t enough, the governor added.

“Greenhouse gases are still being generated and they’re growing,” Brown said. “We have to stop using carbon for our prosperity. Stopping carbon is like stopping a heroin addiction.”

In 2015, California helped found the Under2 coalition, made up of countries, states, cities and regional governments that have pledged to limit greenhouse-gas emissions to 2 tons per capita or 80 percent to 95 percent below 1990 levels by 2050.

On Tuesday, Brown announced that Canada and Mexico have joined the group. Earlier this week, Sweden joined the coalition.

“The governments in the Under2 coalition, like California, are leading the fight against climate change,” said Catherine McKenna, Canadian minister of environment and climate change, who joined Brown at the conference.

But with carbon a major part of everything from plastic chairs to fuels of all types, “de-carbonizing” the world is not going to be easy.

“I don’t know much science … but I’ve studied politics for at least 50 years,” Brown said. “The market is powerful, but we need other things. That’s why we have regulations.”

President Trump’s declaration that climate change is a hoax invented by the Chinese to hamstring U.S. manufacturing doesn’t make it any easier to change the country’s direction, Brown said.

“If there’s any hoax, it’s in the White House, not Beijing,” the governor said. Trump’s statements “are so implausible and stupid it takes your breath away. If you can say that, you can say anything.”

California can’t worry about what is or isn’t coming from Washington, but instead needs to be “pioneering our new way forward,” Brown said. “We have to go against the flow and rechannel the flow because the flow is leading us to catastrophe.”

That sort of forward-looking imagination doesn’t come easy to politicians.

As politicians, “our job is to find out what people want and give it to them,” he said. But now, “we have to look out at the world, see where we’re going and not go there.”

When people see what’s at stake, they will respond, the governor promised.

“Whatever the flimflam artists are saying, we have to overcome it,” Brown said. “We’re not getting there yet … so don’t relax.”